The invention relates to apparatus for and a method of winding layers of wire on a rotor or stator of an electric generator or motor.
It has been proposed hitherto to wind wire around the poles of a rotor or stator using winding apparatus comprising a needle through which the wire passes which is reciprocable alongside the poles and movable past ends of the poles. Examples of such apparatus are shown in U.S. Pat. Nos. 4,612,702 and 4,991,782. In the arrangements described, the wire is wound in a random manner around the poles (known in the art as "scramble winding") one of the objects being to dispense with winding shoes or forms (referred to herein as "winding shields") which are normally required to ensure that the windings are guided around the ends of the poles.
In both of the above prior specifications, the wire to be wound is of a relatively thin type, typically up to around 0.4 mm in diameter and the outlet in the needle for the wire in each case can be many times greater than the diameter of the wire making the needle cheap to produce. All that is required to guide the wire out of the needle is the provision of a polished trumpet or similar outlet at the end of the needle through which the wire can pass. With scramble winding, there is no requirement that the windings be "layered", that is arranged in a number of specific layers, each being formed by winding a much thicker wire, e.g. over 1.2 mm in diameter, so that the turns in each layer are accurately wound side by side in a parallel fashion.
The scramble winding machines shown in the above specifications are not suitable for layer winding and it has been proposed hitherto to utilise a machine having a heavy duty needle which is controlled by computer in order to ensure the accurate placing of the wire in layers as described above. The heavy duty needle is invariably of large transverse cross section in view of the substantial thickness of the wire to be wound and so as to be resistant to bending. That, in itself, can create problems when there is only a narrow gap between the poles around which the wire is to be wound. In such cases, and particularly in newer designs of electric generators and motors, the width of the needle becomes the restricting factor in relation to the thickness of wire which can be wound. Also the wire exits the needle at 90 degrees and the needle must be of sufficient thickness to accommodate the forming of a radius over which the wire passes as it exits the needle. If the radius is insufficient, damage is caused to the insulation coating on the wire which can adversely affect the reliability of the finished product. An object of the present invention is to provide an improved apparatus and method for winding layers of wire on a stator or rotor of an electric generator or motor.
According to one aspect of the invention there is provided apparatus for winding layers of wire on a pole of a rotor or stator of a rotary electric generator or motor, the apparatus comprising a needle mounting member movable substantially axially of the rotor or stator and a needle rotatably mounted on the mounting member and extending transversely thereto, the needle being rotatable about an axis transverse to the direction of movement of the mounting member and having an outlet path for the wire to one side of the axis of rotation of the needle.
According to another aspect of the invention there is provided a method of winding layers of wire on a pole of a rotor or stator of a rotary electric generator or motor comprising the steps of providing a needle having an outlet path for wire to be wound in layers, moving the needle over a winding path and causing the needle to rotate at positions in the winding path.
With an arrangement or method according to the invention, the needle can turn naturally with the wire to follow a winding pattern when the winding direction changes from laying wire along one side of the pole to laying wire across an end. Therefore, it is possible to give the needle a substantial dimension in the direction of winding movement of the needle to make the needle particularly resistant to bending due to the drag of wire thereon as it exits the needle over the outlet path. At the same time, the needle can be given a much smaller dimension in a direction transverse to the winding direction to enable it to pass through a narrow gap between adjacent poles. The invention, therefore, reduces substantially the problems encountered with previously known needles and the method provides the advantages of the speed of machine winding with the accuracy and controllability of hand winding.
Preferably, the path comprises a groove at the distal end of the needle, the groove extending away from the needle axis. In use, the groove will tend to extend in the winding direction because the wire exiting the needle over the groove will tend to steer the needle to follow the winding pattern. In effect, the tension in the wire as it is wound around the pole will tend to create a kind of castor action on the needle.
The needle is preferably arranged so that a first section thereof is mounted in bearing means to facilitate rotation thereof and a second section thereof extends from the first section to one side of the axis of rotation of the needle, the second section having the distal end at which the path is formed.
In a preferred embodiment, the apparatus is combined with a winding shield on the pole which projects beyond an axial end of the pole to keep the wire wound thereon in place during the winding process. In such a case, the needle is arranged to make contact with the shield preferably as the needle changes from winding the wire on one side of the pole following movement of the needle axially of the stator or rotor to winding the wire on an end of the pole. The contact between the shield and the needle is preferably arranged to turn the needle about its axis of rotation by 90 degrees.
As the needle changes from winding the wire across the end of the pole to winding the wire along the other side of the pole, the needle and the winding shield are preferably arranged to make contact with each other again, the contact being arranged to turn the needle again about its axis of rotation preferably by up to 90 degrees.
The use of the winding shield to turn the needle is most useful in that it is not necessary to rely upon tension in the wire alone to turn the needle so that it will follow the winding pattern. Moreover, by using the winding shield in that way, the needle will be correctly orientated for each winding step in a winding cycle prior to beginning that step. Because the needle follows closely around the shields, the amount of travel required of the wire feeder bar is decreased, thus speeding up the winding of each stator. The winding shields also hold the conductor wire in position while the winding process takes place.
It is possible to dispense with winding shields on stators where insulators project above the windings and are of sufficient strength to act in place of a winding shield. In the winding of rotors it is only necessary to use winding shields if the configuration of the pole tip is not suitable for making contact with the needle during winding. On rotors with fixed pole ends the wire is supported by the pole tip during winding.